March 2, 2013

Prosecutors and some lawmakers have long pushed for laws that would set a strict blood-level limit for THC, the key ingredient in cannabis. A driver over the limit would be deemed guilty of driving under the influence, just as with alcohol....

But what's the level that's comparable to the blood alcohol level that's deemed to be too much impairment? It shouldn't just be arbitrary!

Though research and opinions vary widely, studies have shown that smoking marijuana tends to affect spatial perceptions. Drivers might swerve or follow other cars too closely, as well as lose their concentration and suffer from slowed reaction times....

Every state bars driving under the influence. But convictions in drugged-driving cases generally rely on police officers’ observations rather than blood tests. The White House in a drug policy paper last year called on states to adopt blood-limit laws in an effort to reduce drugged-driving incidents by 10 percent by 2015.

There are so many things that impair driving — sleepiness, distraction, low intelligence — why single out anything (including alcohol) for a special law as opposed to relying on observation of actual impaired driving? You could say single out the things that are measurable in the blood. Or you could say: Alcohol deserves to be singled out the way it is because there is a huge, specific, and much-studied problem.

How are people who use marijuana supposed to know when they're over the limit? With alcohol, the products are labeled and there is at least some rough information about the number of drinks and the amount of time that must pass before you can drive. What if you had a drink with dinner and then couldn't figure out whether it was legal to drive the next morning? Isn't that what will happen with marijuana? You'll have no idea what your blood level is, even days later.

Or will there be little blood test kits so you can check? Will the government provide all sorts of labeling requirements for marijuana? They might make legal marijuana production very expensive by requiring predictable calibration of THC and accurate labeling. Then the product could be very expensive, and lots of sales tax could be collected. Isn't that the real puzzle: how to regulate and collect taxes when you've got a product that already thrives as contraband?

But THC is detectable in the blood for a short time, usually a few hours because it is rapidly metabolized.

Or will there be littleblood test kits so you can check?

Because marijuana stays in the bloodstream for a short time, blood tests for marijuana are usually not used, except in the case of automobile accidents and some roadside sobriety check points. Blood or saliva tests can show current intoxication. However, unlike blood alcohol concentration tests, they do not indicate a level of intoxication or impairment.

It's eight hours from bottle to throttle for pilots. If it was 24 hrs, almost no planes would be in the sky, especially fighter planes. That's in the US. I understand that in France, it is quite common for private pilots to drink while flying--or it was a few years ago.

Interesting question. With alcohol, I agree, the limit is arbitrary. I am a big guy (thought continuing to slim with low carb diet) and .07 for me would be a lot more booze than I should have to drive while a slim friend who drinks more often would be fine.

The states have had to falsify drunk driving statistics by counting as drunk driving deaths all people who died in car accidents where any person, not just the driver, had any trace of alcohol in their system. So if a designated driver is run over by a bus full of sober nuns and all die, they are all drunk driving deaths. Without this lying, there would not be enough drunk driving deaths to get upset about from a statistical point of view.

So how do you determine too stoned to drive? Like with alcohol, tolerance makes a huge difference. A pot head could drive at levels that would trip out the casual user. Of course, due to the manipulation of the drunk driving statistics, it is likely that the governments will not be interested in science and safety, just income from tickets.

Michael K, ken in sc:When I was training for my PP-SEL, my personal rule was 24 hours bottle-to-throttle (and the bottle was beer). My father, a senior NASA pilot, used a 12 hour rule, and his consumption was typically a G&T or a glass of wine.But drinking WHILE FLYING? Wow.Flying in CAVU conditions, mostly there's nothing to do. It's much easier than driving a car. No traffic to speak of, autopilot on, etc. But when things go wrong, you're going to need all your brain cycles to stay safe.Among other things, my father did a lot of accident investigation / re-creation, usually asking the question: Could this failure have been recovered by pilot action? The answer was frequently Yes, but almost always with the caveat that the crew had only a FEW SECONDS to do the RIGHT THINGS to survive.I just can't wrap my head around the idea that anyone could think that drinking was compatible with piloting.

On the other hand, I have seen 2 studies by the US National Highway Traffic Safety Administration as well as one by the Australian govt (don't remember if it was the national or a state govt) that found no effect.

The US study had drivers actually drive cars around an obstacle course without any MJ and then smoking more and more MJ. The MJ came from a US govt farm in Missouri(?) and THC levels were calibrated.

Anyone have any links to any studies showing impairment?

One of the NHTSA studies is here:

http://www.erowid.org/plants/cannabis/cannabis_driving4.shtml

I've not looked. Is anyone aware of any studies that did show impairment?

Not just suppositions but actual toking up and measuring driving skills.

There are so many things that impair driving — sleepiness, distraction, low intelligence — why single out anything (including alcohol) for a special law as opposed to relying on observation of actual impaired driving?

The answer to that question is this: if you rely on detectable impairment, you aren't able to throw people in prison and confiscate their cars for driving with otherwise-undetectable "impairment".

The California standard is 0.08. At that level of "impairment" you are substantially less "impaired" than a mother with kids in the car, or a person driving home after a hard day's work.